This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the presently described embodiments. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present embodiments. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
In order to meet consumer and industrial demand for natural resources, companies often invest significant amounts of time and money in finding and extracting oil, natural gas, and other subterranean resources from the earth. Particularly, once a desired subterranean resource such as oil or natural gas is discovered, drilling and production systems are often employed to access and extract the resource. These systems may be located onshore or offshore depending on the location of a desired resource.
Offshore drilling platforms often include hoisting systems for raising and lowering equipment. In some instances, these hoisting systems take the form of cranes used to load and unload equipment from an offshore platform. Of course, cranes and other hoisting systems can be used onshore as well. Cranes often include hoisting lines that are spooled from drums, reeved over sheaves in upper blocks at fixed locations in booms of the cranes (e.g., at the ends of the booms), and are connected to loads via lower, traveling blocks (or hook assemblies) at the ends of the hoisting lines. When raising connected loads with cranes, care is taken to avoid contact between the upper and lower blocks. Such contact, which is referred to as two-blocking, can interfere with crane operation and lead to failure of a hoisting line or disconnection of the suspended load from the hoisting line. Various anti-two-block sensing devices have been used on cranes to help avoid two-blocking.